1. Field of the Invention
This invention is directed to electrodes for alkali metal based electrochemical devices that contain electrically conductive fibers, which may have been metallized, chopped into short lengths and mixed with other components to form the electrodes.
2. Description of the Prior Art
Electrochemical devices such as electric batteries of the solid state type consist of at least an anode, a layer of electrolyte, and a cathode. Batteries require a base current collector and carrier for both the anode and the cathode, which is in contact with an electrode. Various materials have been proposed for use in the electrodes, such as metal foil, powdered metal, mats of woven or non-woven fabric, but none of them are entirely satisfactory.
In Japanese Patent NO. 55-39180 (A) a method of production for the electrode base of a cell is described. A porous member such as felt or non-woven cloth of polypropylene, or polyethylene is immersed in a binder solution that contains conductive powder such as nickel, iron, or carbon powder. The porous member is dried, and electrolytic galvanization with nickel is performed to obtain a nickel layer on the member. The whole Japanese patent structure including powder is metallized after coating.
In the U.S. Patent to Drews et al., U.S. Pat. No. 5,139,902, an electrode is described which comprises a grid plate, which serves as the carrier for battery active material and for current supply and return. The grid plate includes woven plastic threads which are rendered electrically conductive by coating with a conductive layer of metal, and additionally metallized by coating with at least one coating of a lead-tin alloy or lead alone.
Examples of other prior art structures are shown and described in the U.S. Pat. No. to Balanger, U.S. Pat. No. 3,485,677; Rippel, et al., U.S. Pat. No. 4,275,130; Basu, U.S. Pat. No. 4,304,825; Bannister, U.S. Pat. No. 4,471,37; Suguichi, et al., U.S. Pat. No. 4,496,638; Murray, U.S. Pat. No. 4,497,883; Skotheim, U.S. Pat. No. 4,529,086; Hope, et al., U.S. Pat. No. 5,350,647; U.S. Pat. No 4,576,883; Kejha U.S. Pat. No. 5,750,289; Alamgir, et al., U.S. Pat. No 5,747,195 and in the article by Hooper, et al. titled "Advanced Battery Development" published by Odense University Press, 1984.
The described electrochemical devices for which composite electrodes are described and for which the present electrodes are useful include alkali metal batteries, lithium-ion batteries, capacitors and fuel cells.